Underwater noise by way of example during offshore pile driving work can be perceived over great distances by marine mammals, by way of example porpoises and seals. Porpoises in particular are affected by underwater noise since with these animals their hearing is used for navigation and searching for food in addition to communication. Permanent damage to their hearing can in the case of these animals consequently lead to their death.
Different techniques are known for reducing the sound. In the case of a bubble curtain compressed air tubes are placed around the underwater construction site. These are connected to compressors and pump compressed air into the tubes on the sea bed. This compressed air rises in the form of a curtain of air bubbles and thus forms a physically acoustically sound-absorbing barrier.
Instead of the air bubbles which are volatile and difficult to regulate, balloons of elastic material can also be used as sound-reducing elements. A plurality of sound-reducing elements is thereby disposed on a support structure. This is by way of example a net which can be stretched flexibly round the source of the sound in the water. The nets are secured on the sea bed by weights. The complete unit of the sound-reducing elements with the support structure is called a hydro sound damper. A hydro sound damper provides additional damping action and can be matched exactly to the anticipated sound spectrum. A hydro sound damper is less susceptible to sea currents and has the optimum effectiveness in the entire relevant frequency range. Furthermore in the case of a hydro sound damper a continuous supply of compressed air is not required, unlike in the case of the bubble curtain.
In order to reduce the hydro sound a hydro sound damper is known from the printed specification DE 10 2008 017 418 A1. This hydro sound damper consists of a plurality of damping elements spaced from one another to reduce the hydro sound and arranged spread out on a support structure, by way of example on a net. The support structure is arranged at the installation site around a source of noise. A source of noise is by way of example a pile which is introduced into the sea bed, which can be achieved by pile driving or boring.
The printed specification WO 2013/102459 A2 describes a method and a device for handling a hydro sound damper in the region of an offshore construction site, more particularly in the case of a pile which is to be introduced into the sea bed. The disclosed device comprises a holding device on which a first end of the hydro sound damper is held, while a second end of the hydro sound damper which is remote from the first end of the hydro sound damper can be positioned movable relative to the holding device, more particularly at a distance from the holding device.